The present invention relates to a method of and apparatus for imaging the surface of an object at high temperature. More particularly, the invention pertains to a method of and apparatus for imaging the surface of an object at high temperature, most suitable for use in observing an object at high temperature in various industries or the surface condition of the object, for example, observation of the combustion state in a blast furnace or the state of molten iron and slag therein, the burning process of a combustion furnace burner, or the change of the surface condition of a steel ingot in a heating furnace or a steel ingot being hot-rolled.
When it is necessary to observe the high temperature object precisely, for example, microscopic particles such as soot in a fire flame or the surface condition of an object heated to high temperature, employment of spontaneous light radiated from the object permits only a red-hot image thereof to be obtained, and therefore, the obtained image only makes it possible to determine the profile of the object to be observed. If the ambient temperature is especially high and the entire surroundings are in an approximately red-hot state, it is difficult to determine even the profile of the object. In such a case, it is conventional practice to externally irradiate the surface of the object with an intense beam of light and to observe the surface of the object by the use of the reflected light from the surface. By this conventional method, however, it is not possible to obtain a precise observation, since there is a high level of background light noise caused by radiation.